The 21-year-old Chinese national, buoyed by a rubber ring, had been swimming at Shirahama Ohama beach at around 7:30 pm on Monday with a friend, according to the coast guard.
Authorities launched a search and rescue operation after her friend raised the alarm at the beach in the central Shizuoka region that same evening.
“It was around 7:55 pm on July 8 when we received the information after the woman’s friend reported her missing to a nearby convenience store,” a local Japan coast guard official stated.
The woman, whose name was not disclosed, told rescuers that she was swept out to sea and could not return to the beach as she was swimming with a rubber ring.
She was finally spotted floating off the southern tip of Chiba’s Boso peninsula by a cargo ship at 7:48 am on Wednesday, the official said.
Two crew members of a smaller nearby tanker were contacted by radio and jumped into the sea to rescue her.
“There are 80 km in a straight line [between the beach and the rescue spot] … but it is assumed she drifted for an even greater distance,” the official added.
The woman was taken to the hospital after the rescue but did not need to be admitted as she was clear-headed and her dehydration was not life-threatening.